SIZE-FRACTIONATED PRIMARY PRODUCTIVITY 377 



into smaller fragments, which are apparently undamaged. The 

 chlorophyll concentration was unaffected (98.5% of FRB), however. 

 Therefore either the power plant stimulated photosynthesis in this 

 fraction or the results are related to the method of fractionation. 



Rousar (1973) reported a mean productivity rate of 

 9.6 mg C m~^ hr~^ at an inshore Wisconsin station. Our estimates 

 were 9.3 and 8.6mgCm~^ hr~^ at stations FRB and KD, 

 respectively. This indicates that power-plant operation has not 

 radically altered productivity rates in the surrounding region. Rather, 

 deaths of individual phytoplankton caused by entrainment were 

 balanced by natural processes of population growth. We also 

 calculated that, at most, only 0.41% of the nearshore water (0 to 

 30 m in depth) could pass through the plant annually. 



Natural variability poses a significant obstacle to determining 

 small changes in productivity or chlorophyll a. Carpenter, Anderson, 

 and Peck (1974) stated that inabihty to detect changes in photo- 

 synthetic rates could be caused by sampling error or patchiness or 

 could be because there was no actual difference. They also concluded 

 that for chlorophyll a 88 rephcates would have to be taken to detect 

 a ±5% change. Similarly, 22 replicates were required for a ±10% 

 change and 6 replicates for a ±20% change. 



The fact that the unfractionated productivities at the pre- and 

 postcondenser stations were virtually identical and were not signifi- 

 cantly different statistically was a very strong indication that the 

 power plant was not affecting the phytoplankton. Any differences 

 observed between the stations were probably negligible when the 

 precision of sampling techniques and analytical procedures is taken 

 into account. Statistical tests indicate that if certain components of 

 the phytoplankton were affected, whether by stimulatory or 

 inhibitory action, it would be those having dimensions < 10 and 

 > 64 [ira. 



This discussion presents the pertinent facts regarding the effects 

 of power-plant operation on primary productivity at the Kewaunee 

 Power Plant. Some of the statistical results suggest that plant 

 operation may be injurious to individual phytoplankton passing 

 through the cooling system, but the effect on populations is 

 negligible. Furthermore, any observed changes could be artifacts of 

 the methods used in the study. If they are real, the effects are small 

 and detectable only by statistical techniques. Indeed, they may not 

 even be as significant as such natural perturbations as wave action 

 during storms. 



The lack of any obvious effects on the phytoplankton is 

 probably a result of several factors. The ambient temperatures of 



